Rotational cutting apparatuses are traditionally utilized for a variety of material removal processes, such as machining, cutting, and drilling. For example, tungsten carbide cutting elements have been used for machining metals and, to some degree, on drilling tools for drilling subterranean formations. Similarly, polycrystalline diamond compact (PDC) cutters have been used to machine metals (e.g., non-ferrous metals) and on subterranean drilling tools, such as drill bits, reamers, core bits, and other drilling tools. Other types of cutting elements, such as ceramic (e.g., cubic boron nitride, silicon carbide, and the like) cutting elements or cutting elements formed of other materials have also been utilized for cutting operations.
Drill bits used for drilling solid materials may include drill bit bodies to which cutting elements are attached. The drill bit bodies are often formed of steel or of molded tungsten carbide. In some situations, drill bits employing cutting elements may be used in subterranean mining to drill roof-support holes. For example, in underground mining operations, such as coal mining, tunnels must be formed underground. In order to make the tunnels safe for use, the roofs, floors, and/or ribs of the tunnels must be supported to reduce the chances of a roof cave-in and to shield mine workers from various debris falling from the roof.
In order to support various portions of a mine tunnel, boreholes may be drilled into a roof, floor, and/or rib of the mine tunnel using a drilling apparatus. Bolts may then be inserted into the boreholes to anchor support panels to the desired portions of the mine tunnel. The drilled boreholes may be filled with resin prior to inserting the bolts, or the bolts may have self expanding portions, in order to anchor the bolts. A drilling apparatus used for drilling boreholes may include a drill bit that is attached to a distal end of a drill steel. Conventional drill steels typically have a long shaft extending between the drill bit and a rotational portion of the drilling apparatus. The drill steel may enable drilling of boreholes that are significantly longer than the length of the drill bit alone.
Various constraints, such as limited working spaces in mine tunnels, drilling apparatus limitations, and difficulties associated with transporting relatively long drill steel lengths, may necessitate the use of two or more drill steels to drill a borehole to a sufficient depth. For example, a first drill steel may be used to drill a portion of a borehole. Without removing the drill bit and the first drill steel from the borehole, a second drill steel may be connected to an exposed end of the first drill steel, forming a drill shaft having a length approximating the combined lengths of the first and second drill steels, enabling a longer borehole to be drilled
Conventional drill steels may be connected to a drill wrench or chuck of a drilling apparatus. The drill steels may be driven by an external drive mechanism in the drill wrench or chuck. For example, an exterior of a drill steel may have a hexagonal shape designed to fit within a wrench socket having a corresponding hexagonal shape. A drill wrench may be rotated by a chuck that is driven by a power unit. When two or more drill steels are connected to each other during drilling operations, outer surfaces of the drill steels may be exposed to the formation being drilled. The exposed surfaces of the drill steels may be damaged by abrasive surfaces of the formation, causing significant wear to the outer drill steel surfaces. Such wear may reduce the useful life of the drill steels.
For example, hexagonal-shaped outer surfaces of the drill steels may become rounded, making it difficult or impossible to drive the drill steels with a drill wrench or chuck having a hexagonal-shaped socket. Additionally, the worn outer surfaces of the drill steels may cause the drill steels to become caught in the drill wrenches or chucks, making it difficult to remove the drill steels from the drill wrenches or chucks. Problems associated with worn and damaged drill steel surfaces may cause delays in drilling operations. Avoiding such delays may reduce unnecessary downtime and production losses. Avoiding such delays is particularly important during bolting and securement operations in mine tunnels due to various safety hazards present in these environments.